Current supply device



Aug- 25, -1931 J. w. FlTz GERALD y yCURRENT SUPPLY DEVICE Filed Nov. 6, 1925 Patented Aug. 25, 193i UNITED STATES PATENT OFFICE JOHN W. FITZGERALD, OF SHOREWOOD, WISCONSIN ASSIGNOR T BRIGGS STRATTON CORPORATION, 0F MILWAUKEE, WISCONSIN, A CORPORATION 0F WISCONSIN CURRENT SUPPLY DEVICE Application led November 6, 1926, Serial No. 1.46.4725.

This invention relates to certain new and useful improvements in means and circuit arrangements whereby a source of current, such as ordinarily used for lighting pur- 6 poses, may be utilized to supply the necessary current for operating a radio receiver without reproducing a hum or other audible noise therein, and relates more particularly to a battery eliminator of 'the character described in Letters Patent No. 1,774,261, is-

sued August -26, 1930 whereinthe current for the radio receiver is drawn directly from arectifying circuit having means therein'to iron or smooth .out the current impulses and a condenser for supplying current to the receiver during the interval between the current supplying periods of the rectifier.

This invention has as one of its objects the provision of means operable upon variation in the line voltage to maintain the -current delivered by the rectifier substantially constant.

Another object of this invention resldes 'in the provision of 'a thermallyvactuated means adapted to be iniuenced by current variations in the rectifying circuit voltage due to an increase in the service line voltage to impose resistance in the service line and waste the increase of current to pull down the output of the rectifier to the desired degree.

A more specific object of this invention resides in the provision of a current device of the character described, wherein the transformer is so built and designed that its output at the lowest service line voltage is suiiicient to run the rectifier at the desired amperes, and having means actuated from the rectifier circuit for imposing resistance in the service line in the event the current in the rectifying circuit increases due to an increase in the service line voltage whereby current increases in .the service line are waste vthrough the resistance. Y.

Wit the above and other objects in view which will appear as the description proceeds, my invention resides in the novel'c'onstruction, combination and arrangement of parts substantially as hereinafter described and more' particularly defined by the` appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come Within the scope of the claims.

In the accompanying drawings, I have illustrated one complete example of the physical embodiment of my invention constructed according to the best mode I have so far devised for the practical application of the principles thereof, and in which Figure 1 is a diagranunatical illustration of an apparatus and circuit embodying my invention;

Figure 2 is a view, partly in side elevation and partly in section, of my improved device or regulating the current delivered the transformer from the servicehline, and 1 Figure 3 is a transverse sectional view taken through Figure'2 on the .plane of the line 3 3.

The circuit illustrated in the accompanying drawings is adapted for alternating leurrent and the numerals .5 and 6 designate an alternating current service line such as Athe 110-volt circuit ordinarily used for lightin purposes in residences, which are connecte, as at 7 and 8, with the movable contacts 9 andA 10 of a relay 11 and engageable with stationary contacts 12 and 13, res ectively, upon energization of the core 14 o? a choke device 15, to be later described. The stationary contacts 12 and 13 are electrically connected with the primary winding 16 of a transformer 17 by conductors 18 and 19, res ectively, and inductively associated with t e primary winding 16 is a secondary winding 20.

One end 21 ofthe secondary winding is connected with one sideof the filament 22 of a rectifying bulb 23 by a conductor 24, the other side of the filament beingconnected with the secondary winding at an intermediate point 25 by a conductor 26. The other end 27 of the secondary'fiwindin is connected with the positive side'bf the lament circuit 28 of a radio receiver, dia ammatically illustrated as 29, by a con uctor nsI 30, the negative side 31 of the radiofilament which is connected with the plate 35 of the rectiying bulb through ,a conductor 36, a

Winding through the conductor 30. As the A operation of the electrolytic condenser or choke coil 37 ofthe device generally is clearly and at length described in my copending application above referred to, reference is directed thereto for more detailed explanation.

The transformer 17 is so built and designed that its output at the lowest average line Voltage, say, ninety volts, is sufficient to so run the rectiying bulb that its output is of the desired amperes and, as the output of the rectifying bulb is directly in pro ortion to theline voltage, means are provi ed for .Wasting the excess of current so that the curv rent delivered by the rectifier remains subtantially constant at all line voltages.

Asillustrated, the conductor 18 leading to thev primary winding'l is cut and has one Aend 40 connected with. one end of an adjustable resistor 41 and `its other end 42 connected with the other end of the resistor 41 through a pressure applying lever and contact member 43. The lever 43 is pivoted at 44 between a paix,` of spaced lu s or ears 45 and has its free end 46 provide with a contact button 47 which engages the resistor 41. For the purpose of illustration, the resistor has been illustrated as a stack of resistor discs confined within a tube or housing 48 mounted on the supporting base or panel 49 andan expansil s ring 50 normally urges the free end of the ever out of engagement with the resistor to tend to release the pressure on the resistor whereby maximum resistance is offered to the passage of current therethrough;

Two bracket members 51 and 52 are xed to the panel 49 and have a wire of metal having a relatively high coefficient of expansion stretched therebetween above the lever 43 and in longitudinal alignment therewith. One end of the wire 53 is fixed to the bracket' member 51, as at 54, and the otherend thereof is connected, as at-55, with a screw 56 adjustable in the bracket member 52, the screw 56 providing means for adjusting the tautness of the wire when contracted. The wire passes through a pressure applying member 57 of insulating material -which projects below the wire suiiicient to a ply a pressure on the free end of the lever wlhen the wire is taut to compress the reslstor 41 and decrease its resistance value to a minimum.

Theconductor 30 of the rectifying circuit is cut and one end 58 thereof is electrically connected with the upright 52 and the other end 59 electrically connected with the upright 51 so that the current of the rectifying circuit flows through the wire 53. The resistor 41 being imposed in the conductor 18, as above described, the current from the service line flows therethrough to the transformer primary winding.

The screw 56 is normally adjusted so that the wire is taut to apply maximum pressure to the resistor 41 and retain its resistance to the passage of current therethrough to a minimum, and with the device in operation, as at length described in my aforementionedV application, the service current flows through' the resistance 41 and the rectified current through the wire 53, the latter bein heated by the current flowing therethroug The tautness of wire 53 is so adjusted that with. the out ut of the rectifying bulb when the line vo tage is, for example, ninety volts little ,change is effected in the resistance 41. However, upon an increase in the line volt- Yage above the minimum at which thetrans-4f.,

former is designed, the current delivered by the rectifying bulb increases a proportional degree and, as a result, the temperature of the wire 53 increases, causing it to stretch. As the wire 53 stretches; the pressure on.. the lever 43 likewise releases permitting in the spring 50'to move the lever 43 outwardly to decrease the pressure on the resistance 41, wasting the excess of line current through the resistor. Likewise when the line voltage. decreases, the current delivered by the rectifying means likewise drops cooling wire 53, proportionately and causing the same to contract and appl added pressure on the lever 43 against t e spring 50 to increase,A the pressure on the resistor 41 and reduce its resistance tothe passage of the line current to the transformer primary winding.'

From the fore oing description taken in connection with t e accompanying drawings it will be'readily apparent to those skilled in the art to which an invention of the character described appertains, that I proylde novel .and efficient means .,for. maintainlng the service current supplied the. trans-1 former substantially constant so that the rectified current is likewise constant.

What I claim as my invention is:

1. A device of the character described, comprising a rheostat, a member for controlling the resistance of the rheostat,'means normally urging said member toward onei posltion, a thermal member normally taut Y between fixed supports, and. means connecting the medial portion of the thermal member with said member to hold the same against its urging means, the expansion of said thermal member under the influence of temperature changes permitting the movement of said member byits urging means. 2. A device of the character described, comprising a rheostat, a member for controlling the resistance of the rheostat, means normally urging said member toward a polo sition to increase the resistance of the rheostat, a thermal member normally taut between spaced stationary supports, and means controlled by the thermal member and'engaging the first member to hold the same agamst its urging means, the expansion of the thermal member under the inluence of temperature changes\permtting the movement of said first member under its urging means to increase the resistance of o the rheostat.

3. Adevice of the'character described, comprising a compressible rheostat, a member engageable wlth the rheostat for controlling its resistance, athermal element' normally taut between spaced stationary supports and disposed over said member, means positioned between the thermal element and the said member whereby the said member is maintained in a predetermined 30 position with respect to the com ressible rheostat, and spring means yielda l urging the said member toward the t ermal element whereby expansion of the thermal element permits the spring means to move the member to change the resistance of the rheostat.

4. A device of the character described, comprisin a compreible rheostat, a pivoted memer having its free end engageable with the rheostat to adjust the resistance thereof, a thermal element normally taut between spaced stationary supports and disposed above'said pivoted member whereby the free end of the pivoted member is heldY against the compressible rheostat to maintaina predetermined resistance value, and spring means yieldably urgingr the free end of the pivoted member away om the rheostat against the action of the thermal element, whereby expansion ofthe thermal element permits movement of the free end of the pivoted member away from the compressible rheostat to effect a change in its resistance value.

In testimony whereof I hereunto alix my signature.

J OHN'W. FITZ GERALD. 

